全文获取类型
收费全文 | 11951篇 |
免费 | 1133篇 |
国内免费 | 1404篇 |
专业分类
化学 | 610篇 |
晶体学 | 3篇 |
力学 | 493篇 |
综合类 | 359篇 |
数学 | 10469篇 |
物理学 | 2554篇 |
出版年
2024年 | 21篇 |
2023年 | 116篇 |
2022年 | 138篇 |
2021年 | 233篇 |
2020年 | 236篇 |
2019年 | 326篇 |
2018年 | 315篇 |
2017年 | 367篇 |
2016年 | 442篇 |
2015年 | 301篇 |
2014年 | 623篇 |
2013年 | 893篇 |
2012年 | 561篇 |
2011年 | 705篇 |
2010年 | 630篇 |
2009年 | 897篇 |
2008年 | 878篇 |
2007年 | 889篇 |
2006年 | 796篇 |
2005年 | 680篇 |
2004年 | 566篇 |
2003年 | 574篇 |
2002年 | 545篇 |
2001年 | 397篇 |
2000年 | 427篇 |
1999年 | 368篇 |
1998年 | 332篇 |
1997年 | 297篇 |
1996年 | 195篇 |
1995年 | 103篇 |
1994年 | 111篇 |
1993年 | 63篇 |
1992年 | 57篇 |
1991年 | 45篇 |
1990年 | 28篇 |
1989年 | 41篇 |
1988年 | 30篇 |
1987年 | 15篇 |
1986年 | 15篇 |
1985年 | 33篇 |
1984年 | 38篇 |
1983年 | 16篇 |
1982年 | 31篇 |
1981年 | 21篇 |
1980年 | 30篇 |
1979年 | 13篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
M. Amar D. Andreucci R. Gianni C. Timofte 《Journal of Mathematical Analysis and Applications》2021,493(2):124533
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation. 相似文献
2.
Clemens G. Raab Georg Regensburger Jamal Hossein Poor 《Journal of Pure and Applied Algebra》2021,225(5):106564
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials. 相似文献
3.
4.
Wacker oxidation is an industry-adopted process to transform olefins into value-added epoxides and carbonyls. However, traditional Wacker oxidation involves the use of homogeneous palladium and copper catalysts for the olefin addition and reductive elimination. Here, we demonstrated an ultrahigh loading Cu single atom catalyst(14% Cu, mass fraction) for the palladium-free Wacker oxidation of 4-vinylanisole into the corresponding ketone with N-methylhydroxylamine hydrochloride as an additive under mild conditions. Mechanistic studies by 18O and deuterium isotope labelling revealed a hydrogen shift mechanism in this palladium-free process using N-methylhydroxylamine hydrochloride as the oxygen source. The reaction scope can be further extended to Kucherov oxidation. Our study paves the way to replace noble metal catalysts in the traditional homogeneous processes with single atom catalysts. 相似文献
5.
6.
7.
8.
Inner derivations and norm equality 总被引:3,自引:0,他引:3
Mohamed Barraa Mohamed Boumazgour 《Proceedings of the American Mathematical Society》2002,130(2):471-476
We characterize when the norm of the sum of two bounded operators on a Hilbert space is equal to the sum of their norms.
9.
Nobuaki Obata 《Acta Appl Math》1997,47(1):49-77
A general theory of operators on Boson Fock space is discussed in terms of the white noise distribution theory on Gaussian space (white noise calculus). An integral kernel operator is generalized from two aspects: (i) The use of an operator-valued distribution as an integral kernel leads us to the Fubini type theorem which allows an iterated integration in an integral kernel operator. As an application a white noise approach to quantum stochastic integrals is discussed and a quantum Hitsuda–Skorokhod integral is introduced. (ii) The use of pointwise derivatives of annihilation and creation operators assures the partial integration in an integral kernel operator. In particular, the particle flux density becomes a distribution with values in continuous operators on white noise functions and yields a representation of a Lie algebra of vector fields by means of such operators. 相似文献
10.
HIRONOBU Ishihara 《Geometriae Dedicata》1997,67(3):309-336
Several classification results for ample vector bundles of rank 2 on Hirzebruch surfaces, and on Del Pezzo surfaces, are obtained. In particular, we classify rank 2 ample vector bundles with c2 less than seven on Hirzebruch surfaces, and with c2 less than four on Del Pezzo surfaces. 相似文献